The field of the present invention is reciprocating air motors.
Devices having double pistons and diaphragms driven by compressed air directed through an air motor are well known. Reference is made to U.S. Pat. Nos. 8,360,745; 5,957,670; 5,213,485; 5,169,296; and 4,247,264; and to U.S. Patent Publication No. 2014/0377086. The disclosures of the aforementioned U.S. Patents and patent publication are incorporated herein by reference in their entirety. These air driven diaphragm pumps employ air motors using feedback control systems to provide reciprocating compressed air for driving the pumps.
Common among many of such prior devices directed to air driven diaphragm pumps is the presence of an air motor housing having air chambers facing outwardly to cooperate with pump pistons and diaphragms coupled by a common shaft. Outwardly of the pump diaphragms are pump chamber housings, inlet manifolds and outlet manifolds. Passageways transition from the pump chamber housings to the manifolds. Ball check valves are positioned in both the inlet passageways and the outlet passageways. An actuator mechanism associated with the air motor housing between the air chambers includes the common shaft reciprocating therethrough and coupled with the diaphragms located between the air chambers and pump chambers by central pistons.
The actuator between the air chambers for air driven pumps commonly includes a directional control valve that controls air flow to alternate pressure and exhaust to and from each of the air chambers, resulting in reciprocation of the pump. The directional control valve is controlled by a pilot system controlled in turn by the position of the pump diaphragms or pistons. Thus, a feedback control mechanism is provided to convert a constant air pressure into a reciprocating distribution of pressurized air to each operatively opposed air chamber.
Actuators defining reciprocating air distribution systems are employed to substantial advantage when shop air or other convenient sources of pressurized air are available. Other pressurized gases are also used to drive these products. The term “air” is generally used to refer to any and all such gases. Driving products with pressurized air is often desirable because such systems avoid components which can create sparks. The actuators can also provide a continuous source of pump pressure by simply being allowed to come to a stall point with the pressure equalized by the resistance against the pump. As resistance against the pump is reduced, the system will again begin to operate creating a system of operations on demand.
A vast variety of materials of greatly varying viscosity and physical nature are able to be pumped using such systems. In using such actuators to drive such pumps, greatly varying demands can be experienced. Viscosity of the pump material, suction head or discharge head and desired flow rate impact operation. Typically the source of pressurized air is relatively constant. In U.S. Pat. No. 8,360,745 a mechanism for predictably adjusting flow restriction is disclosed. In U.S. Patent Publication No. 2014/0377086, flow restriction is created responsive to pump position. With variations in pump loads and inlet flow restrictions, the feedback control mechanism of air motors can result in stalling of the actuator mechanism during shifting of the directional control valve.